Growth hormone is produced in the pituitary and secreted into the bloodstream where it binds to growth hormone receptor (GHR) on many cell types, causing production of insulin-like growth factor-1 (IGF-1). IGF-1 is produced mainly in the liver, but also in adipose tissue and the kidney, and secreted into the bloodstream. Several disorders, such as acromegaly and gigantism, are associated with elevated growth hormone levels and/or elevated IGF-I levels in plasma and/or tissues.
Excessive production of growth hormone can lead to diseases such as acromegaly or gigantism. Acromegaly and gigantism are associated with excess growth hormone, often caused by a pituitary tumor, and affects 40-50 per million people worldwide with about 15,000 patients in each of the US and Europe and an annual incidence of about 4-5 per million people. Acromegaly and gigantism are initially characterized by abnormal growth of the hands and feet and bony changes in the facial features. Many of the growth related outcomes are mediated by elevated levels of serum IGF-1.